Sandayū Koma, also called Koma Sandayuu, is a first-year student at Y-Academy, an elite boarding school training those with Yo-kai Special Power (YSP). Defying his family’s esteemed rakugo heritage, he abandoned the traditional art to pursue supernatural studies, qualifying for Y-Academy alongside childhood friend Jinpei Jiba. Their bond formed after Jinpei noticed a "Bizarre Man Beron" keychain on his backpack, sparking a shared enthusiasm for the anime.

Sandayū’s appearance echoes the Yo-kai Komasan, featuring a round head framed by hair mimicking hitodama flames and a backpack styled after Komasan’s furoshiki cloth. A YSP Watch or Majin Watch adorns his left wrist, granting him transformative abilities: Little Kommander with Komadillo, Little Kommander Ace post-training under mentor Zazel, and Zashiki Kommander when aided by Gnomey. These powers make him vital to the YSP Club’s efforts against supernatural threats.

Shy and soft-spoken, Sandayū exhibits gentle politeness and wide-eyed innocence, initially naive to concepts like romance. Though awkward in social guidance, his steadfast kindness and loyalty anchor his relationships, particularly with Jinpei, whose impulsive streak he tempers with quiet resolve. Their partnership navigates challenges through complementary strengths.

Central to Y-Academy’s mysteries, Sandayū battles entities like Onryo and investigates paranormal incidents, such as the school’s seven legends. In *Y School Heroes: Bustlin’ School Life*, he combats bullying and supernatural adversaries using his YSP Watch. As a Rank A Yo-kai in *Yo-kai Watch: Wibble Wobble*, his "Komakoma Hundred Fracture Fist" Soultimate Move targets central Yokai Wib Wobs.

Guided by allies like classmate Mataro Tamada and teacher Haruhiko Usumizawa, Sandayū grows in confidence through teamwork and Zazel’s mentorship, mastering advanced transformations. His fondness for soft serve ice cream mirrors Komasan’s tastes, a nod to their thematic link, yet his human agency and narrative role remain distinct.